[DOCS-509] Explain() works by re-generates the query plan: this can affect timing Created: 10/Sep/12  Updated: 25/Sep/12  Resolved: 10/Sep/12

Status: Closed
Project: Documentation
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: William Zola Assignee: Sam Kleinman (Inactive)
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Participants:
Days since reply: 11 years, 21 weeks, 1 day ago

 Description   

When running a query using the explain() functionality, this will cause the query engine to re-calculate the query plan. This, in turn, can cause some queries to run slower. If you're timing queries, you shouldn't use explain(); if you're explain()ing queries you shouldn't trust the timing.

This is not called out in the documentation.



 Comments   
Comment by auto [ 25/Sep/12 ]

Author:

{u'date': u'2012-09-25T15:48:22-07:00', u'email': u'samk@10gen.com', u'name': u'Sam Kleinman'}

Message: DOCS-509 minor style change
Branch: master
https://github.com/mongodb/docs/commit/56c380676ade1fe04964ce955aa5a37e3558d4ed

Comment by auto [ 25/Sep/12 ]

Author:

{u'date': u'2012-09-25T15:48:22-07:00', u'email': u'samk@10gen.com', u'name': u'Sam Kleinman'}

Message: DOCS-509 minor style change
Branch: master
https://github.com/mongodb/docs/commit/56c380676ade1fe04964ce955aa5a37e3558d4ed

Comment by auto [ 10/Sep/12 ]

Author:

{u'date': u'2012-09-10T11:12:35-07:00', u'email': u'samk@10gen.com', u'name': u'Sam Kleinman'}

Message: DOCS-509 note about timing and explain
Branch: master
https://github.com/mongodb/docs/commit/8ddde6ea096b1b2edb4ddac15e84c28a7529d7a6

Comment by Scott Hernandez (Inactive) [ 10/Sep/12 ]

Yes, explain is not for timing things but only for seeing how they work.

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